Air spring devices, also called air springs for short, which are clamped between the chassis and the vehicle body and which have an air spring bellows which in turn is fastened between an air spring cover and a rolling piston are known in a multiplicity of embodiments. The air spring is at an inner excess pressure during operation. The air spring bellows rolls under load and, in the case of spring movements, with the formation of a rolling fold on the outer contour of the concentric air spring piston/rolling piston. An air spring of this type is used frequently in road or rail vehicles, in order to achieve comfortable suspension.
Here, both air springs exist, in which the air spring bellows forms a rolling fold only on one side, namely as a rule on the rolling piston, or air springs, in which the rolling bellows is clamped between the air spring cover and the rolling piston with the formation of a two-sided (rolling) fold. Air springs with a one-sided rolling fold can often be found in passenger cars, while the air springs with a two-sided rolling fold which are often larger and more supportive are installed rather in trucks and rail vehicles.
In order to achieve a sufficient load-bearing capability of the entire system in the case of relatively thin rolling bellows, the rolling bellows or the air springs or dampers can be provided with what are known as outer guides, namely with a tubular sleeve as “supporting corset” or supporting body which surrounds the rolling bellows. Thus, for example, a thin rolling bellows can be optimized to high internal pressures and therefore high load-bearing capacities with a simultaneously satisfactory harshness behavior by way of a thin lightweight metal sleeve as supporting body. Here, the outer guides are configured and arranged in such a way that the rolling bellows can roll on one side on the outer side of the rolling piston and on the other side on the inner surface of the outer guide.
When, in particular, air springs are arranged in the chassis region of vehicles, folding bellows are often used which surround the air springs partially and by way of which, for example, the rolling fold is protected which is sensitive to contaminants. Foreign bodies, such as thrown-up stones or pieces of tar from the road surface, can namely damage the rubber skin of the rolling bellows fold considerably and reduce the service life.
The use of folding bellows of this type does not entail any particular problems, as long as air springs with integrated and coaxially arranged dampers can be used in the case of relatively generous overall heights and the usual installation position is provided for the air spring, in which position namely the air spring cover is situated at the top and the rolling piston is situated at the bottom. Here, the rolling fold points “downward”. A folding bellows can then be fastened easily to the lower end of the sleeve which serves as outer guide and toward the bottom to the damper. Fastening of this type to the damper permits a sufficient “working length” which does not overextend the elasticity of the folding bellows.
On account of the small amount of installation space present in modern vehicles, however, it is often necessary to install air springs without integrated dampers in the overhead position. The dampers are then installed, for example, separately next to the air springs, which of course can reduce the “overall height” of the chassis considerably. In this installation position which is also known under the designation “upside down installation”, the rolling piston, situated above, is supported on the vehicle body, while the air spring cover rests below on, for example, a transverse link of an axle. In this installation position, the rolling fold is directed upward and an annular gap, that is to say an annular “pocket”, is formed between the outer guide and the rolling piston, which annular gap necessarily has to be closed by a folding bellows, since otherwise foreign bodies can collect immediately in said pocket and cannot fall out again as a result of gravity. However, the fastening of the folding bellows between the outer guide and the damper, which fastening has proven itself in the customary installation position, is then out of the question on account of the low overall height, since the damper is then attached next to the air spring. A sufficient “working length” which does not overextend the elasticity of the folding bellows is therefore not available here.